Basic and applied research is described, the goal of which is to develop a microcomputer-based navigation aid for the visually impaired. The device will (a) inform a visually impaired traveler of his or her current location and orientation with respect to the environment being navigated, (b) provide information about the proximal surroundings, and (c) assist in route planning. Portable GPS (satellite based Global Positioning System) receivers will be used to determine the traveler's longitude and latitude, and a computerized database will contain information about environmental features at and around that location. A primary consideration in designing the system will be to promote independence on the part of the visually impaired traveler. Experiment and questionnaires will be used to evaluate alternatives in the design of the system. Among the design alternatives to be considered is the type of display. Experiments will compare navigation performance and user evaluations when using a virtual auditory display to those when using a display providing verbal instructions. The virtual display will indicate the positions of landmarks by having their labels, spoken by speech synthesizer, appear as sounds at the correct locations within the auditory space of the traveler. Basic experimental research will pursue two general issues, one concerning inherent limitations on navigation without sight and one investigating the implications --positive or negative -- of device-aided navigation for learning about complex environments.